Smokeless briquettes



3,093,463 Patented June 11, 1963 ice 3,03,463 SMOKELESS BRIQUETTESDaniel Garrick Madley, Twyning, near Tewkesbury, England, assignor toCoal Industry (Patents) Limited, London, England, a company of GreatBritain No Drawing. Filed June 13, 1960, Ser. No. 35,438 4 Claims. (Cl.44-10) This invention relates to improvements in the manufacture ofsmokeless briquettes without a binder.

It is known that briquettes can be made without a binder from cokingcoal if this coal is first heated, before briquetting, to a criticaltemperature in which the coal is in a plastic or globulated condition.However, the briquettes so made are not smokeless and moreover thetemperature is so highly critical that maintenance of the temperature atthe correct value is extremely diflicult; consequently such proposalshave not hitherto resulted in a commercially valuable process.

An object of the present invention is to render it possible to produce ahard smokeless briquette without a binder in a relatively simple manner.

For this purpose according to the invention a weakly or non-coking coalin comminuted form is formed into a char by being heated rapidly underuniform heating conditions so as to remove a part of the volatilecontent, and the resultant char is briquetted while still hot, with noor relatively small loss in temperature. The uniform heating conditionsare obtained by heating the coal while in the form of a fluidized bed.

The temperature at which the char is produced is usually within therange 350-S C. and preferably 370470 C. and the briquetting may beeffected by extrusion. Such extrusion may include an expansion by usingfor example an extrusion nozzle of which the cross-section increases inthe direction of movement of the material as is, for example, describedin prior copending application Serial No. 689,947, now abandoned. Thecross-sectional area of the extrusion nozzle is preferably controlled inaccordance with the resistance to movement of the material through thenozzle and this may be done manually or may be efiected automatically asdescribed in the said co-pending application Serial No. 689,947.

The non-coking coals referred to are of Ranks 20 0, 700, 800 and 900according to the British Standard Coal Classification.

The term char used herein is intended to denote a coal from which someof the volatile constituents originally present have been removed. Byrapidly is meant a process in which the conversion into char is effectedin less than one hour, for example 1020 minutes, as compared with thegenerally-known processes in which the production of char requires manyhours and may take up to 24 hours. The uniform heating conditions aresuch that the temperature of the hot char discharged into the outletfrom the heater system does not show considerable variation across thesection of said outlet e.g. a variation of not more than say 10-20 C.;in practice it has been found that such variation in the case of heatingin a fluidized bed is very much smaller and within 1-2 C.

It is also important that the temperature to which the coal is heatedshall be capable of accurate control is. to within :5 C.; for thatreason a fluidized bed is used.

It is preferable that the temperature of the hot char should not besubstantially reduced after it has been made and before it isbriquetted, and for this purpose any external piping through which thechar is led to the briquetting press may be thermally insulated. It isalso preferable for the briquetting press or the extrusion nozzlethereof to be initially heated e.g. electrically. Although in many casesa relatively small temperature drop may be permissible, in general anypossible loss in temperature before briquetting should preferably notexceed 50 C. as otherwise the briquettes may not be of satisfactoryquality. It has been found that the greater the drop in temperature thelower the strength of the briquette and the greater is the dustiness ofthe briquette; in some cases according to the nature of the coal undertreatment it may be possible to tolerate a larger temperature drop withonly a relatively small decrease in quality. It is, however, essentialthat the char should be treated while still hot and in general the lowerthe temperature drop the higher will be the quality of the briquetteproduced.

The briquetting temperature may be higher than the temperature at whichthe char has been made provided this temperature does not exceed themaximum permissible temperature for the particular coal under treatment.

The raw coal may be mixed with coke or coke breeze before being heatedto form a char and the briquettes mad-e may be rendered still harder andespecially suitable for metallurgical purposes by being heatedpreferably soon after formation and in any case while still hot-tohigher temperatures eg 8501,000 C.

The hot briquettes made by any of the processes above described may becooled slowly in a controlled manner in an atmosphere containing apredetermined amount of oxygen.

It is also to be understood that the hot char, instead of beingbriquetted by extrusion, may also be briquetted by any other knownmethod and in particular by any of the methods or apparatus described inprior Patents Nos. 2,809,395 and 2,860,957.

By way of example the following applications of the invention aredescribed with reference to particular ranks of coal according to theBritish Standard Coal Classification.

Example I A Baddesley coal of Rank 902 size -10 B.S.S., and having avolatile content, dry ash free, of 37% was formed into a char in a fluidbed with a residence time of 10 minutes at a temperature of 425 C. andbriquetted at that temperature at a pressure of 6 /2 tons/square inch,the hot briquettes being quenched with water. The density of thebriquettes formed was 1.32, the volatile content dry ash free 24.4% andthe strength 166 lbs./ square inch. The briquettes were a high gradesmokeless fuel suitable for an open grate.

Example II Example III A Calverton coal of Rank 903 was formed into achar in a fluid bed with a residence time of 10 minutes at a temperatureof 425 C. and then briquetted at the same temperature. The briquettes soformed were subsequently carbonized at a temperature of 850 C. resultingin a high density briquette having a density of 1.41. suitable formetallurgical use.

The briquettes were a high grade smokeless fuel spesaes Example IV ABetteshanger coal of Rank 203 was formed into a char in a. fluid bedwith a residence time of 10 minutes at a temperature of 485 C. andbriquetted at the same temperature. The briquettes so formed had avolatile content of 17.1%, the volatile matter of the original coalbeing 12.4%. The briquettes were a high grade smokeless fuel suitablefor a closed stove.

I claim:

1. A method for the manufacture of smokeless briquettes without a binderwhich comprises the steps of heating, for a period of time not exceedingone hour, a comminuted non-coking coal While in the form of a fluidizedbed to a temperature within the range 350-500" whereby the coal isconverted into a char and a relatively minor part of the volatilecontent is driven off, subsequently removing said char from thefluidized bed and delivering said char to a briquetting press whilestill hot but in a condition in which the conversion to char has beensubstantially completed, the decrease between the temperature of thefluidized bed and the temperature of the char at the entry to thebriquetting press being not more than 50 C.

2. A method according to claim 1 wherein the briquetting press is anextrusion press and the extrusion is effected through an extrusionnozzle of variable crosssection.

3. A method according to claim 1 wherein the briquettes, after leavingthe briquetting apparatus, are heated to a temperature within the range850 to 1,000 C.

4. A method according to claim 1 wherein coke is mixed with the coal andthe mixture is subsequently heated to form a char.

References tilted in the file of this patent UNITED STATES PATENTS905,693 Grifiin Dec. 1, 1908 2,117,179 Kopp May 10, 1938 2,168,889Thomas Aug. 8, 1939 2,321,238 Piersol June 8, 1943 FOREIGN PATENTS291,543 Great Britain June 77, 1928 616,857 Great Britain Jan. 27, 1949

1. A METHOD FOR THE MAUFACTURE OF SMOKELESS BRIQUETTES WITHOUT A BINDERWHICH COMPRISES THE STEPS OF HEATING, FOR A PERIOD OF TIME NOT EXCEEDINGON HOUR, A COMMINUTED NON-COOKING COAL WHILE IN THE FORM OF A FLUIDEZEDBED TO A TEMPERATURE WITHIN THE RANGE 350-500* WHEREBY THE COAL ISCONVERTED INTO A CHAR AND A RELATIVELY MINOR PART OF THE VOLATILECONTENT IS DRIVEN OFF, SUBSEQUENTLY REMOVING SAID CHAR FROM THEFLUIDIZIED BED AND DELIVERING SAID CHAR TO A BRIQUETTING PRESS WHILESTILL HOT IN A CONDITION IN WHICH THE CONVERSION TO CHAR HAS BEENSUBSTANTIALLY COMPLETED, THE DECREASE BETWEEN THE TEMPERATURE OF THEFLUDIZIED BED AND THE TEMPERATURE OF THE CHAR AT THE ENTRY TO THEBRIQUETTING PESS BEING NOT MORE THAN 50*C.